Method and apparatus for filling and sealing plastic containers

ABSTRACT

In a method of pressurizing and filling a plastics-film pouch through an aperture in its walls, and subsequently sealing a patch over the aperture, while the pouch is held with the aperture in sealing contact with a surface, the use of a surface of specified curvature for supporting the patch during sealing.

United States Patent [191 Cayton et al.

[ METHOD AND APPARATUS FOR FILLING AND SEALING PLASTIC CONTAINERS [75]Inventors: Kenneth Cayton, Welwyn Garden City; Grahame Melvin Reade,Wheathampstead, both of England [73] Assignee: Imperial ChemicalIndustries Limited, London, England [22] Filed: Mar. 15, 1973 [21] Appl.NO.: 341,605

[30] Foreign Application Priority Data Mar. 28, 1972 United Kingdom14451/72 [52] US. Cl 53/22 B; 53/112 B [51] Int. Cl B65b 31/04 [58]Field of Search 53/22 B, 112 B [451 Apr. 15,1975

[56] References Cited UNITED STATES PATENTS 2,638,963 5/1953 Frederick53/28 X 3,745,024 7/1973 Ford et al 53/22 B X Primary Examiner-Travis S.McGehee Attorney, Agent, or FirmCushman, Darby & Cushman [57] ABSTRACTIn a method of pressurizing and filling a plastics-film pouch through anaperture in its walls, and subsequently sealing a patch over theaperture, while the pouch is held with the aperture in sealing contactwith a surface, the use of a surface of specified curvature forsupporting the patch during sealing.

7 Claims, 8 Drawing Figures METHOD AND APPARATUS FOR FILLING AND SEALINGPLASTIC CONTAINERS This invention relates to a method and apparatus forproducing a package comprising a sealed flexible plastics container withcontents'including a gas at superatmospheric pressure.

The invention relates particularly to the filling and sealing offlexible plastics containers containing liquids under pressure,including liquids containing dissolved gases, such as beer andcarbonated soft drinks, and liquids which are packed under pressure of agas that is not soluble in the liquid, to give substantially rigidpacks. It may be applied also to the packaging of solid articles, thepack being pressurized to make it rigid, usually for the purpose ofprotecting the contents or to improve the sale appeal of the pack, andto the packaging of particulate solids. The invention includes the filling of the container with gas alone under superatmospheric pressure.

In application Ser. No. 271,208 filed Dec. 7, 1972, we have describedand claimed a method of producing a package comprising a sealed flexibleplastics con tainer, with contents including a gas at superatmosphericpressure, that comprises: locating an aperture in the wall of the closedcontainer over an orifice in a substantially smooth surface, saidorifice being connected to a source of a gas at super-atmosphericpressure; inflating the container by the introduction of said gas whilethe container wall surrounding said aperture is held substantially ingas-tight contact with said surface; and, while said container is stillfully inflated and in gastight contact with said surface, sliding italong relative to said surface to bring that portion of the wall of thecontainer which surrounds said aperture into contact with a supportedflexible sealing strip held in substantially continuous relationship tosaid surface; and sealing the sealing strip to the wall of the containeraround said aperture, by applying heat if necessary.

The term over an orifice includes any case where the container islocated so that the aperture covers the orifice. irrespective of whetherthe surface containing the orifice is generally located above, beneathor beside the container. The expression closed container" means that thecontainer is gas-tight, in respect of the pressure of gas to be reachedwithin the container, except at the aperture provided for pressurizingthe container and at any further aperture in the wall of the containerthat may be held in gas-tight contact with a surface and sealed insimilar manner to the aperture described. The term fully inflated meansthat the pressure inside the container is at least sufficient to enable7 the container wall to be pneumatically held in substantially gas-tightcontact with the surface.

When the container is to be filled with a liquid or particulate solid,this is preferably introduced through the aperture after the containerhas been inflated with gas. It may be introduced through the sameorifice as the gas, or through a closely adjacent second orifice that isalso covered by the aperture in the container, or through a secondorifice spaced from the first orifice, to which the inflated containermay be slid after it has been pressurized at the first orifice. When thepackage is to contain a solid article or articles these are preferablyput into the container before it is closed, and the container issubsequently pressurized and sealed in the manner described.

The method of the invention is used with particular advantage in thepackaging of beer and carbonated soft drinks in flexible plasticscontainers.

The invention of application Ser. No. 271,208 filed Dec. 7, 1972 furtherprovides apparatus for performing a method as described, that includes asmooth surface having therein an orifice; means for supplying a sealingstrip in such a manner that it may be drawn from its source of supplyalong a path on said surface, or on a second surface substantiallycontinuous therewith and in line with the orifice; means for supplyingthrough the orifice a gas for inflating to superatmospheric pressure aplastics film container presented to said surface with an aperture inits wall located over said orifice; means for holding the containersufficiently under compression against said surface or surfaces tomaintain a seal around said aperture, while it is slid along saidsurface or surfaces to bring said aperture into the path of said sealingstrip and until the sealing strip covers and surrounds the aperture;and, if necessary, means for heat sealing the sealing strip around theaperture.

We have now found that, in heat-sealing the flexible sealing strip tothe wall of the container around the filling aperture, the seal can beimproved if the sealing strip and the container wall surrounding theaperture are supported during sealing upon a curved protrusion on thesurface against which the inflated container is held. The seal may thenbe produced without any puckering of the container wall or of thesealing patch, and the seal much improved in strength and reliability.

In accordance with the present invention, therefore, a method as claimedin application Ser. No. 271,208 filed Dec. 7, 1972 is furthercharacterized in that the flexible sealing strip and the container wallsurrounding the aperture are supported, during the sealing of the stripto the wall of the container, upon a surface that follows effectively aconvex curve across each and any diameter of the area supporting theportion of the strip that is to be sealed to the container and thecontainer wall surrounding said portion.

In accordance with a further feature of the present invention, anapparatus as claimed in application Ser. No. 271,208 filed Dec. 7, 1972is further characterized in that the part of the surface that supportsthe portion of the sealing strip that is to be sealed to the container,and the container wall surrounding said portion, during the sealing ofthe strip to the wall of the container, follows effectively a convexcurve across each and any diameter thereof.

Whilst the supporting surface ideally follows a true curve across eachand any diameter thereof, the surface may for ease of machining beshaped across at least one diameter as a series of flats giving theeffect of a convex curve.

The invention will now be more particularly described by way of examplewith reference to the accompanying drawings, which illustrate thefilling of plastics-film pouches with beer, and of which:

FIG. 1 is a side view, seen partly in section, of the filling andsealing apparatus;

FIGS. 2 to 6 show in more detail the shape of the surface upon which theflexible sealing strip is supported in the apparatus of FIG. 1;

FIG. 7 shows schematically the supply-lines for the beer and for carbondioxide for pressurizing the pouches; and

FIG. 8 shows a plastics-film pouch suitable for use in the method of theinvention.

In FIG. 1: l is a magazine of plastics-film tubular pouches to befilled; 2 is a block, suitably of stainless steel, constituting thepressurizing and filling head, provided with a smooth, flat frontsurface, 3, in which are a filling orifice, 4, and concentric with andsurrounding the filling orifice, a pressurizing orifice 5; 6, 7 are apair of blocks, again suitably of stainless steel, separated by a narrowgap, 8, suitably about 0.005 inch wide, and having their smooth, flatfront faces level with that of block 2, the face of block 6 beingcontiguous with that of block 2. Through the gap 8 passes the leadingend of a sealing tape; supplied from reel 9, the tape having aheat-sealable coating on the surface that faces the block 6. 10 is theheat-sealer block, whose front face is of a curved shape to be moreparticularly described, across which passes a heat-sealer element, 11.The heat-sealer block 10, which is of heat-insulating material such as abonded fabric laminate, is separated from block by a narrow gap throughwhich operates a retractable knife, 12. 13 is a chute into which filledpacks are ejected.

Opposite the members just described are a pair of parallel rails, theupper of which is shown at 14, for supporting inflated packs pressedagainst them, and a rod, 15, parallel with the rails 14, upon which isdriven a reciprocating cylinder, 16; to this cylinder are attached twopairs of vertically-spaced pawls for pushing the pressurized and filledpacks to the right (as seen in the drawing), the upper pawls of the twopairs being shown at 17, 18. Also attached to cylinder 16 is areciprocable vacuum-pad, 19, which may be advanced to take aplastics-film pouch, 20, from the magazine, and transfer it, on movementof the cylinder 16 to the right (as seen in the drawing), to a positionagainst the pressurizing and filling block, 2.

The plastics-film pouches, which are closed by gastight seals except fora circular filling aperture in the wall of each, are accurately locatedin the magazine with their filling apertures in a predeterminedposition. Thus, when the apparatus is in operation, successive pouchesmay be indexed by the vacuum pad 19 to a position in which the fillingaperture is opposite and adjacent to the orifices 4, 5 in thepressurizing and filling block 2. When the pouch has been indexed intothis position, carbon dioxide is blown through orifice 5 into the pouch,and the vacuum pad is pushed back by the inflating pouch until the pouchcomes into contact with the rails 14, while the vacuum is cutoff; thecylinder 16 is then returned to its original position, so that thevacuum pad is returned to a position opposite the pouch magazine, andthe pawls 17 are brought past the inflated pack 21 to its rear side.Meanwhile when the pouch has been inflated to the desired pressure, asshown at 21, a metred quantity of beer is pumped into the pouch throughorifice 4, as a jet, carbon dioxide being displaced as the pouch fills.When the flow of beer has stopped and excess has been bled from the feed(as will be later described), the cylinder 16 again advances to theright, and the filled pack 21 is pushed by pawls 17 past the sealingtape supply slot and on until its filling aperture is opposite theheat-sealer element 11; a pack in this position is shown at 22. As thepack advances, the leading end 23 of the sealing tape is carried forwardupon the pack by frictional forces, and further tape is withdrawn fromroll 9, until the tape covers and extends beyond the filling aperture.Thus, on arrival at the heat-sealer 11, the pack has a patch of sealingtape covering its filling aperture. When this movement of the cylinder16 is complete, the heatsealer switches on, the knife 12 advances to cutthe tape, and the tape becomes securely sealed as a patch over thefilling aperture of the pack. Meanwhile, the cylinder 16 moves back,bringing pawls 18 past the pack shown at 22 to its rear side. At thenext forward movement of cylinder 16, pawls l8 push the filled andsealed pack from the heat-sealer and on until it drops into chute 13.From the chute 13 the successive packs may pass to a sleeve-wrappingdevice.

The shape of the heat-sealer block 10 is shown in FIGS. 2 to 6 of which:FIG. 2 is a plan; FIGS. 3 and 4 are side and end views respectively; andFIGS. 5 and 6 are sections through A,A and B,B of FIG. 2, respectively.The pack approaches the heat-sealer blocks as shown in FIG. 2 from theleft-hand side. In a particular example of a heat-sealer block as shownin FIGS. 2 to 6, and suitable for use in sealing a pack formed from atubular-film pouch having a flat width of mm, the surface shape isproduced by a transverse spherical curvature of 31.75 mm on which isimposed, longitudinally, a flat from the left-hand side as shown, at anangle of 8, and a flat from the right-hand side at an angle of 5,separated by a 0 flat 10 mm in length at the position of the heat-sealerelement 11, the three flats giving an effective radius of curvature,from a line perpendicular to the center point of the 10 mm flat, ofapproximately 92.5 mm.

Suitable curvatures for heat-sealer blocks for sealing packs ofdifferent sizes may be determined by experiment. Generally, the largerthe diameter of the pack, the larger are the preferred curvatures of theheatsealer block.

In FIG. 7 are shown schematically the supply lines for the carbondioxide and beer. As previously indicated, the gas and beer are suppliedto the pouches through concentric orifices; for simplification andclarity, however, the two supply systems are shown in FIG. 7 on separatesides of the pack. Both systems provide for any carbon dioxide and beerentering the pouches to be maintained in a substantially sterilecondition.

In FIG. 7, 21 represents the pouch being pressurized and filled, 24 theline to the supply source of carbon dioxide. which is suitablymaintained at a pressure of about 20 psi, and 25 the line to the beersupply, suitably maintained at a pressure of about 30 psi. For thecarbon dioxide line 24, 26 is an on/off valve, 27 a nonreturn valve, and28 the line to orifice 5 (FIG. 1); while 29 is a line to a drain,through non-return valve 30 and pressure-relief valve 31, the latterbeing set at 20 psi or other pressure desired in the filled pack. Forthe beer line 25: 36 is a non-return valve; 37 is a metering pump,suitably a diaphragm pump; 38 is an on/off valve and 39 a two-way valve;and 40 is a bleed line for beer remaining beyond valve 39 after a packhas been filled, this bleed line leading to a drain via on/off valve 41,non-return valve 42 and restrictor valve 43. In operation, the on/offvalve 26 for the carbon dioxide is turned on for the initial inflationof the pouch, and remains on until just before the filled pack is movedfrom block 2 and slid along to be heat-sealed. When the pouch has beenpressurized, the measured amount of beer is pumped into it through line25. As the beer is fed into the pouch carbon dioxide is displacedthrough non-return valve 30 and pressure-relief valve 31. When fillingis complete, and to prevent beer remaining in the line between valve 39and the filling orifice from blowing out when the pack is moved, andwetting the surface of block 2 (FIG. 1), 2-way valve 39 is turned to itssecond position, and bleed valve 41 is turned on for a time sufficientto empty this remaining beer to the drain, which is at atmosphericpressure, an excessive pressure drop being prevented by restrictor valve43.

In order to ensure that substantially sterile conditions may bemaintained, the parts of lines 28 and 29 between the non-return valves27 and 30 and the pressurizing orifice, and the part of line 25 betweenthe twoway valve 39 and the filling orifice, are made as short aspossible.

Although FIG. I has been described as a side view, the apparatus is infact arranged during operation so that the surface 3 is in a downwardlyfacing position indined at a small angle to the horizontal. Thecontainer may then be sufficiently filled with the beer, but a gas spacestill left under the filling aperture until the aperture has beensealed. The presence of this gas space allows the surface of thecontainer to be kept dry while the container is filled; it alsofacilitates heat sealing, since the loss of heat through the gas is muchless than if a liquid were in contact with the film. The apparatus issuitably tilted until surface 3 is at an angle of about 45 to thehorizontal.

In FIG. 8 is shown a plastics-film pouch suitable for use in the methodof the invention. This is a preferred form of pouch produced in themanner described in our copending Application Ser. No. 311,154, filedDec. 1, 1972, which describes a method of closing an open end of aplastics-film container that comprises forming an elongated heat-sealbetween the flat, opposed layers of the plastics film at or towardstheir edges and along the whole length of said open end, folding the endof the container over, inwardly of the seal, so that the heatseal lieswholly against the external surface of one wall of the container, andadhering the folded-over end in such position by means ofa stripofflexible material adhered over the edge region of the folded-over end,along substantially the whole length thereof, and extending beyond theinner edge of the heat-seal, and to the adjacent portion of thecontainer wall. In the preferred method a reinforcing ribbon is firstadhered to the outer side of the seal, extending beyond its edge, andthe strip of flexible material extends over the fold of the folded-overend with its ends projecting beyond the sides of the container, theopposed edges of the strip being adhered one to the other in thisregion. In FIG. 8: 34 is the flat, empty plastics-film pouch; 35 is thefilling aperture in its wall; 46 is the heat-sealed, folded-over end; 47is the edge of the seal-reinforcing ribbon; and 48 is the strip offlexible material extending over the fold of the folded-over end, theprojecting ends of the strip, adhered together, being shown at 49. Whenthe pouch has been filled and sealed it assumes a cylindrical form overthe major part of its length, but has chisel-shaped, or saddle-shaped,ends as indicated in the packs shown at 21, 22 in FIG. 1.

Various modifications may be made in the method and apparatusparticularly described. For example, other methods may be used forpresenting the pouches to the pressurizing and filling surface, or otherarrangements may be made for sliding the filled packs from one stationto the next. Or the filled packs may be slid longitudinally instead oftransversely from the filling to the sealing station. The surfacesagainst which the packs are slid need not necessarily be flat, providedthat they are sufficiently smooth to allow such sliding. They may, forexample, form parts ofa cylindrical surface. For contents other thancarbonated liquids, a gas other than carbon dioxide may be used,particularly nitrogen.

Types of plastics'film pouches other than that particularly describedmay be used provided that they are of sufficient strength, are formedwith gas-tight seals, and are provided with a filling aperture in theirwall.

The nature of the plastics material forming the pouches will be chosenin accordance with the intended pressure to be enclosed or developedwithin the pack. For high pressures such as those exceeding 15 psi,pouches formed of biaxially oriented polyethylene terephthalate film areespecially suitable, particularly when coated with a heat-scalable,gas-impermeable coating, for example a coating of vinyliden e chloridecopolymer. The coating may be an external coating or an internalcoating.

The adhesive used for sealing the filling aperture must also be chosento suit the pressure it will have to withstand. Hot melt adhesives,particularly when used on a plastics film of the same type as used forthe construction of the container, are generally preferred. Particularlysuitable hot melt adhesives include those based on copolymers of two orall of the acids sebacic, terephthalic and isophthalic acid condensedwith ethylene glycol. Hot melt adhesives based on ethylene/vinyl acetatecopolymers are also suitable. It is also possible to use for sealing thefilling aperture a sealing strip bearing a pressure sensitive adhesivecoating effective at room temperature.

The filled packs are preferably provided with a sleeve of paper, foil orother flexible sheet material, preferably formed by wrapping or windingaround substantially the whole of the cylindrical part of the pack asheet or strip of the sheet material and securing it by means of anadhesive, such as a moisture-activated adhesive, applied at least to theedges of the sheet. If the sleeve is applied closely to the containerwhile the contents are cold, subsequent slight expansion of thecontainer results in the container walls being firmly supported by thesleeve. This gives added strength to the pack and also provides for itslabelling and decoration. The sleeve may be extended at one end to forma stand. When pouches as shown in FIG. 8 are used, the sleeve preferablyextends just over, the edge of the reinforcing strip 47 at each end ofthe pack, the ends of the adhered edges 48 of the strip being foldeddown upon the walls of the pack when they are covered by the sleeve. Thefinished pack then has a neat appearance, and can be made attractive byprint applied to the sleeve.

We claim:

1. In a method of filling and sealing a flexible plastics container,closed by gas-tight seals except at a filling aperture in its wall, toproduce a package having contents at superatmospheric pressure, byplacing the container against a smooth surface with said aperturelocated over an orifice in said surface, said orifice being connected toa source of gas at superatmospheric pressure and said surface being ofsuch smoothness that the aperture may be sealed thereby against thesubstantial escape of gas when the container is inflated and held withits apertured wall pressed against said surface, in-

flating the container by the introduction of gas through said orificefrom said source of gas, and while holding the inflated container withsaid aperture in substantially gas-tight juxtaposition to said surface,sliding the container along, against and relative to said surface, tobring that portion of the wall of the container which surrounds saidaperture into contact with a supported flexible sealing strip held insubstantially continuous relationship to said surface, and sealing thesealing strip to the wall of the container around said aperture, whilesaid container is substantially in gas-tight juxtaposition to saidsurface: the improvement consisting in that the container is slid alonga surface on which the flexible sealing strip and-the container wallsurrounding the aperture are held during the sealing of the strip to thewall of the container wherein the surface follows effectively a convexcurve across each and any diameter of the area of the strip that is tobe sealed to the container wall.

2. A method as claimed in claim 1 in which, after the container has beeninflated by said gas, but before it is sealed,a liquid is introducedinto the container through said aperture under pressure such that themajor part of the gas is displaced by the liquid, while the displacedgas is concurrently withdrawn from the container.

3. A method as claimed in claim 2 in which the container is filled witha carbonated liquid.

4. In an apparatus for filling and sealing a flexible plasticscontainer, said apparatus comprising a smooth surface having therein anorifice, means for supplying and means for supporting a sealing strip insuch manner that it may be drawn from its source of supply along a pathsubstantially continuous with said surface and in line with but in adirection away from said orifice, means for supplying through saidorifice a gas for inflating to superatmospheric pressure a plastics-filmcontainer presented to said surface with a filling aperture in its walllocated over said orifice, a support means for holding the containersufficiently under compression against said surface to maintain asubstantially gas-tight seal around said aperture while the container isslid along said surface to bring said aperture into the path of saidsealing strip and until the sealing strip covers and surrounds saidaperture, and means for causing sealing of the sealing strip to thecontainer wall: the improvement consisting in that the surface of saidmeans for supporting the sealing strip follows effectively a convexcurve across each and any diameter thereof.

5. An apparatus as claimed in claim 4 in which said orifice is connectedthrough valves to a source of gas at superatmospheric pressure and to asource of liquid stored under superatmospheric pressure.

6. An apparatus as claimed in claim 4 that includes means for heatingthe convexly curved surface of said means for supporting the sealingstrip, such that said surface constitutes a heat-sealer for said sealingstrip.

7. In an apparatus comprising:

1. a smooth surface having an orifice therein;

2, first container moving means for moving a plasticsfilm containerwhich is closed except for an aperture in a wall of the container into aposition such that the aperture is in register with the orifice;

3. gas supply means for supplying to said orifice a gas undersuperatmospheric pressure whereby the container is inflated by the gaspassing through said orifice and aperture into the container;

4. container support means for holding the inflated container undersufficient pressure against said smooth surface so as to maintain asubstantially gas-tight seal around said aperture;

5. second container moving means for moving the inflated containerbetween the container support means and the smooth surface so that theaperture is moved out of register with the orifice but so that theaperture remains in contact with the said smooth surface, therebymaintaining the inflation of the container;

6. sealing strip supply means for supplying a sealing strip in such aposition that the sealing strip is engaged by the container wall andcovers and surrounds the aperture;

7. sealing means having a sealing support surface for supporting thesealing strip and the surrounding portion of the container wall andcausing sealing of the sealing strip to the container wall;

the improvement comprising a sealing support surface which followseffectively a convex curve across each and any diameter thereof.

1. In a method of filling and sealing a flexible plastics container, closed by gas-tight seals except at a filling aperture in its wall, to produce a package having contents at superatmospheric pressure, by placing the container against a smooth surface with said aperture located over an orifice in said surface, said orifice being connected to a source of gas at superatmospheric pressure and said surface being of such smoothness that the aperture may be sealed thereby against the substantial escape of gas when the container is inflated and held with its apertured wall pressed against said surface, inflating the container by the introduction of gas through said orifice from said source of gas, and while holding the inflated container with said aperture in substantially gas-tight juxtaposition to said surface, sliding the container along, against and relative to said surface, to bring that portion of the wall of the container which surrounds said aperture into contact with a supported flexible sealing strip held in substantially continuous relationship to said surface, and sealing the sealing strip to the wall of the container around said aperture, while said container is substantially in gas-tight juxtaposition to said surface: the improvement consisting in that the container is slid along a surface on which the flexible sealing strip and the container wall surrounding the aperture are held during the sealing of the strip to the wall of the container wherein the surface follows effectively a convex curve across each and any diameter of the area of the strip that is to be sealed to the container wall.
 2. A method as claimed in claim 1 in which, after the container has been inflated by said gas, but before it is sealed, a liquid is introduced into the container through said aperture under pressure such that the major part of the gas is displaced by the liquid, while the displaced gas is concurrently withdrawn from the container.
 2. first container moving means for moving a plastics-film container which is closed except for an aperture in a wall of the container into a position such that the aperture is in register with the orifice;
 3. gas supply means for supplying to said orifice a gas under superatmospheric pressure whereby the container is inflated by the gas passing through said orifice and aperture into the container;
 3. A method as claimed in claim 2 in which the container is filled with a carbonated liquid.
 4. container support means for holding the inflated container under sufficient pressure against said smooth surface so as to maintain a substantially gas-tight seal around said aperture;
 4. In an apparatus for filling and sealing a flexible plastics container, said apparatus comprising a smooth surface having therein an orifice, means for supplying and means for supporting a sealing strip in such manner that it may be drawn from its source of supply along a path substantially continuous with said surFace and in line with but in a direction away from said orifice, means for supplying through said orifice a gas for inflating to superatmospheric pressure a plastics-film container presented to said surface with a filling aperture in its wall located over said orifice, a support means for holding the container sufficiently under compression against said surface to maintain a substantially gas-tight seal around said aperture while the container is slid along said surface to bring said aperture into the path of said sealing strip and until the sealing strip covers and surrounds said aperture, and means for causing sealing of the sealing strip to the container wall: the improvement consisting in that the surface of said means for supporting the sealing strip follows effectively a convex curve across each and any diameter thereof.
 5. second container moving means for moving the inflated container between the container support means and the smooth surface so that the aperture is moved out of register with the orifice but so that the aperture remains in contact with the said smooth surface, thereby maintaining the inflation of the container;
 5. An apparatus as claimed in claim 4 in which said orifice is connected through valves to a source of gas at superatmospheric pressure and to a source of liquid stored under superatmospheric pressure.
 6. An apparatus as claimed in claim 4 that includes means for heating the convexly curved surface of said means for supporting the sealing strip, such that said surface constitutes a heat-sealer for said sealing strip.
 6. sealing strip supply means for supplying a sealing strip in such a position that the sealing strip is engaged by the container wall and covers and surrounds the aperture;
 7. sealing means having a sealing support surface for supporting the sealing strip and the surrounding portion of the container wall and causing sealing of the sealing strip to the container wall; the improvement comprising a sealing support surface which follows effectively a convex curve across each and any diameter thereof.
 7. In an apparatus comprising: 